There is known an electroluminescence element which is one of display elements configured to display letters or figures, using their property of emitting light upon application of an electric field to a certain kind of semiconductor material. FIG. 6 shows an arrangement of a prior art electroluminescence element in which reference numeral 1 refers to an insulative substrate made from glass or other material, 2 to a stripe-shaped transparent electrode provided on one surface of the insulative substrate and made from indium tin oxide (ITO), titanium tin oxide or other material, 3 to a first insulative layer covering surfaces of the insulative substrate 1 and of the transparent electrode 2 and made from silicon nitride (Si.sub.3 N.sub.4) or other material, 4 to a fluorescent layer made from zinc sulfide (ZnS) or other semiconductive material, 5 to a second insulative layer similar to the first insulative layer and 6 to a stripe-shaped back electrode opposed to and disposed across the transparent electrode 2 and made from aluminum or other material. Usually, manganese (Mn) or other activator is added to the fluorescent layer 4 to improve the luminescence property.
When an alternating voltage is applied between the transparent electrode 2 and the back electrode 6 in the electroluminescence element having the aforegoing arrangement, the fluorescent layer 4 exhibits light. Therefore, the electroluminescence element can be used as a surface light source, and is practically used as various kinds of flat panel display.
In the arrangement of FIG. 6, however, since the transparent electrode 2 projects from the surface of the insulative substrate 1, it causes an irregularity in crystallization particularly at curved portions 3a and 4a of the first insulative layer 3 and in the fluorescent layer 4 which are deposited on corners 2a of the transparent electrode 2 as shown in FIG. 7 when the first insulative layer 3 and the fluorescent layer 4 are formed by any depositing method. Obviously, this decreases the insulation ability of the first insulative layer 3.
Further, the fluorescent layer 4 is subject to a decrease in the luminescence efficiency and to an increase in the luminescence threshold voltage when an electric field applied thereto concentrates at its curved portions 4a. Additionally, it is impossible to increase the thickness of the transparent electrode 2 because it further increases the length of the corner portions. Therefore, particularly when a large display capacity is attempted in a simple matrix driving system, CR time constant determined by the capacitance C and the resistance R of the transparent electrode 2 increases, and this invites a decrease in the brightness.
Because of these problems, the prior art electroluminescence element is not sufficiently reliable as a product.